Overactive thyroid, also known as hyperthyroidism or thyrotoxicosis, is a condition that occurs when there is too much thyroid hormone in the body. The condition is more common in women than men.
The role of the thyroid gland
The thyroid gland is found in the neck. It produces hormones that are released into the bloodstream to control the body's growth and metabolism. These hormones are called thyroxine and triiodothyronine. They affect processes such as heart rate and body temperature, and help convert food into energy to keep the body going.
Normally, the levels of thyroxine and triiodothyronine in the blood are carefully controlled so that these processes happen at a stable rate.
However, in hyperthyroidism, the thyroid gland produces an excess amount of thyroxine or triiodothyronine, which speeds up the body's metabolism. This causes symptoms such as:
- hyperactivity
- an increased appetite
- sudden weight loss or gain
See Overactive thyroid - symptoms for more information
Overt and subclinical hyperthyroidism
There are several causes of an overactive thyroid gland, although the most common is Graves' disease, in which the body's immune system targets the thyroid gland and causes it to produce too much thyroid hormone.
Once diagnosed, overactive thyroid can be classed as either:
- overt, which means that it causes symptoms, or
- subclinical, when the levels of thyroid hormone are still within normal limits
Outlook
Overactive thyroid can be effectively treated using medicines to slow the production of hormones from the thyroid gland, as well as radiotherapy and in some cases surgery. For more information, see Overactive thyroid - treatment
However, if it is not successfully controlled, overactive thyroid can cause other health problems such as irregular heart rhythms and osteoporosis (weak, brittle bones).
If left untreated, overactive thyroid can be fatal.
